The present invention relates to a manufacturing method for a thin film magnetic head, an inspecting method for a thin film magnetic head, and an apparatus therefor, and particularly to a manufacturing method for a thin film magnetic head, an inspecting method for a thin film magnetic head, and an apparatus therefor including an inspecting step for measuring with high accuracy dimensions of track width of a magnetic recording element in the form of a bar formed from a plurality of elements cut out of a substrate.
Recently, smaller size and larger capacity magnetic recording disk drives have been developed, and at present, small magnetic recording disk drives using a disk having the sizes of 3.5 inch and 2.5 inch have occupied the mainstream. In such a small disk drive as described above, since a rotational speed of the disk is low, where a magnetic induction type magnetic head in which a read output depends on the disk speed is used, the lowering of the read output poses a problem. On the other hand, in a magneto resistive head (hereinafter called GMR head) using a magneto resistive element (hereinafter called GMR element, GMR: Giant Magento-resistive), since the read output does not depend on the disk speed, even the small magnetic recording disk drive whose rotational speed is low is able to obtain a high read output. Further, to provide the magnetic recording disk drive having higher recording density, it is necessary to have a narrower track which narrows the track width of the magnetic head. The GMR head is advantageous in that even in case of narrower track, a high read output is obtained as compared with the magnetic induction type magnetic head. It is contemplated from the foregoing that the GMR head is a magnetic head suitable for smaller size and larger capacity.
So, there has been proposed a laminated thin film head using the GMR head as a read-back head, and a magnetic induction type magnetic head as a recording head, respectively.
On the other hand, in order to realize higher recording density, in case of face recording density of 20 G bit/inch2 of a magnetic disk, it is necessary that track width be about 0.7 to 0.5 micro meter (xcexcm), and in addition, with respect to the accuracy, about xc2x10.07 to 0.05 micro meter (xcexcm) is required.
To exceed 60 G bit/inch2 for higher density, it is necessary that track width be 0.3 micro meter (xcexcm) or less, and with respect to the accuracy, about xc2x10.03 micro meter (xcexcm) is expected to be required. With the narrower track as described, it is has been difficult to inspect a track width in the process of manufacturing thin film magnetic heads.
First, the manufacturing method for the GMR head which is a thin film magnetic head will be described with reference to FIGS. 2(a) to (c). FIG. 2(a) is a top view of a wafer formed with the GMR element. The GMR element is formed by a thin film process represented by sputtering, exposure, ion milling and the like, in accordance with the method not shown. In the embodiment shown in FIG. 2, elements are patterned by a batch exposure, as one unit U. An element formed by the thin film process is cut in the rectangular shape and separated out of a wafer 1. FIG. 2(b) shows a group of elements in the rectangular shape (hereinafter referred to as a bar 2) separated out of the wafer. A single bar 2 is formed with a plurality of, for example, 30 GMR elements 101 (hereinafter referred to as an element 101). FIG. 2(c) shows a slider 100 having the element 101 cut out of the bar 2. The slider 100 is incorporated into the magnetic recording disk drive by the method not shown. The typical method for forming the GMR head is described in Japanese Patent Laid-open No. Hei 8-241504.
FIG. 3 is a sectional perspective view of the GMR head. In the figure, this side of the figure is a floating surface 102 of the element 101 with respect to the disk surface (not shown). An upper magnetic shield film 103 and a lower magnetic shield film 104 perform the action for enhancing signal resolving power. A signal from a magnetic disk (not shown) close to the floating surface 102 is read by a pair of signal detecting electrodes 105. A spacing between the signal detecting electrodes 105 is a read track 106, whose width is a read track width TWR. A write coil 107 is formed on the upper magnetic shield film 10, and a write head 108 is formed above the write coil 107. An extreme end of the write head 108 is a write track 109 whose width is a write track width TWW. These track widths are observed from the floating surface 102 (the arrow in the figure).
FIGS. 4(a) to 4(c) show the detail of the bar 2 after cut. FIG. 4(a) is a view as viewed form the side for carrying out element forming by the film process, that is, from the upper surface, and FIG. 4(b) is a view as viewed from the arrow of FIG. 4(a), that is, from the floating surface side. Various dimensions of the element 101 are measured from this direction. In FIG. 4(b), X-direction is the direction in which the elements 10 are continuously arranged, and Y-direction is the direction at right angle thereto. As described above, the bar 2 is in the rectangular shape; for example, in case of length: 50 mm, height: 15 mm, and thickness: 0.5 mm, the bar 2 is, generally, flexed like a bow as shown in FIG. 4(b) although different depending on the conditions at the time of cutting, and the flexing amount S thereof is often scores of micro meters (xcexcm) in the central part.
FIG. 5 shows the procedure for measuring in accordance with the conventional measuring method. First, the bar 2 is set to observation means such as a microscope in a direction (the floating surface side) of FIG. 4(b) to observe the element 101. First, an image of a first element is obtained, and various element dimensions of the element 101 are computed. In case of not a final element, the bar 2 is moved by 1 pitch in the direction X to obtain an image of a next element. Where an element can be measured, element dimensions are computed. This operation is repeated to find all the element dimensions. However, since the bar 2 is flexed like a bow, it is sometimes that the element is not within the detecting range when an image is obtained merely by movement in the direction X, making it impossible to measure the element dimensions. In this case, it is necessary that to enable measurement of the element dimensions, the element is moved in a direction in which the bar 2 is flexed, that is, in the direction Y so that the element is within the detecting screen. Further, where a nanometer order is detected, an aberration of an optical system need also be taken into consideration. To this end, it is necessary accurately locate an element in the center of a field of view of an objective lens for which an optical aberration is best corrected.
This will be explained in more detail with reference to FIGS. 6(a) to (c). FIG. 6(a) is an image in which a first element is detected. Since it is necessary for detecting of element dimensions with high accuracy to detect the element 10 in an enlarged scale, a field of detecting of an image is about 20 micro meters (xcexcm). The height of the element 101 is approximately 10 micro meters (xcexcm). For example, the bar 2 is set in the direction Y so as to assume a height Y1 position within the measuring range 111. The bar 2 is stepwise moved in the direction X in order to detect next element as previously mentioned. FIG. 6(b) shows an image of an element in the vicinity of the center. Within the measuring range 111, the element 101 is detected downward due to the flexure of the bar 2 to assume a height Y2. Since in this state, the element 101 is not within the detecting range 111, it is impossible to measure element dimensions. Therefore, the bar 2 is moved in the direction Y, and moved so that the element 101 assumes a height Y3 within the measuring range 111, as shown in (c). As described above, in the conventional observing system, the element 101 is outside the detecting range due to the flexure of the bar 2 merely by the movement in the direction X, and therefore, observing means such as the bar 2 or a microscope is moved to a sensible position to compute element dimensions, thus taking two times or more for obtaining an image and for the computing time.
As a method for measuring element dimensions, there is a method that uses an optical microscope or a photo electric conversion sensor, and multiplies an area obtained from brightness data of a signal obtained from the photo electric conversion sensor by a suitable coefficient to obtain a desired width, as described in Japanese Patent Laid-Open No. Hei 10-82616.
FIG. 7 shows the procedure of element dimensions computing processing in the conventional apparatus. A focal position of observing means such as a microscope is adjusted to a camera, after which the camera is exposed to detect an image. The image is subjected to photo electric conversion and transferred to a memory. As described above, an element position is confirmed; and if element dimensions can be detected, various dimensions are computed. The result is displayed, after which the bar is moved in the direction X to detect a next element. This operation is shown as the measuring time of one element 500. As described above, where element dimensions cannot be detected in the vicinity of the central part of the bar, the bar is moved in the direction Y and a focal point of an optical system is adjusted again to a camera, after which an image of an element is detected. This operation is repetitively carried out until dimensions of an element can be detected. This operating time 501 is added to the measuring time of 1 element. When this computing processing flow is applied, each processing is performed in series, and therefore the measuring time is prolonged, failing to perform efficient measurement. Further, reduction in measuring time becomes difficult, and when exposure time of a camera is changed due to the change in light quantity, the measuring time is to change, failing to perform stabilized measurement.
In the method described in the prior art, where a bar formed with a plurality of elements is measured continuously, a position of an element becomes deviated vertically and is forced out of the detecting range, thus making it necessary to grasp the position of an element on all such occasions to correct it. To measure all the elements, several detectings per element are necessary, thus increasing the time required for the measurement of elements. Further, since movement of a bar, locating and the like are repeated, the detecting reproducing properties are also lowered. Further, since computing processing of elements is processed in series, the detecting time is prolonged, failing to perform efficient measurement.
According to the embodiments of the present invention described below, there can be provided a manufacturing method for a thin film magnetic head, an inspecting method for a thin film magnetic head, and an apparatus therefor including an inspecting step for measuring, efficiently, stably, and with high accuracy, dimensions of a track width of a magnetic recording element in the form of a bar formed by a plurality of elements cut out of a substrate.
That is, according to the present invention, the manufacturing method for a thin film magnetic head as described hereinafter is provided.
First, the invention disclosed in the embodiment is characterized by a manufacturing method for a thin film magnetic head comprising the steps of: forming a plurality of thin film patterns corresponding to a plurality of thin film magnetic head elements on a substrate; cutting the substrate formed with the plurality of thin film patterns to cut out a group of thin film magnetic head elements; measuring dimensions of a predetermined part of the thin film patterns for the group of thin film magnetic head elements separated; selecting a group of good thin film magnetic head elements on the basis of the result of measurement; and feeding the group of good thin film magnetic head elements selected to the next step wherein in the step of measuring dimensions, the thin film patterns are image-picked up, and the dimensions are measured from images of the thin film patterns obtained by image-picking up.
Preferably, in the inspecting step, dimensions corresponding to a track width of the thin film magnetic head are measured, the measurement of dimensions corresponding to the track width is carried out for all the thin film magnetic head elements constituting the group of thin film magnetic head elements, and the group of thin film magnetic head elements in which the dimensions corresponding to the track width are within the predetermined range is fed as the good product to the next step.
Preferably, in the inspecting step, dimensions corresponding to a track width of the thin film magnetic head are measured, and the measurement of dimensions corresponding to the track width is sequentially carried out for all the thin film magnetic elements constituting the group of thin film magnetic head elements.
Preferably, when the measurement of dimensions corresponding to the track width is sequentially carried out for all the thin film magnetic head elements constituting the group of thin film magnetic head elements, a position of a thin film magnetic head element to be measured next is estimated from positional information of the thin film magnetic head element measured previously.
The present invention further is characterized by a manufacturing method for a thin film magnetic head comprising the steps of: forming a plurality of thin film patterns corresponding to a plurality of thin film magnetic head elements on a substrate; cutting the substrate formed with the plurality of thin film patterns; image-picking up a section of the substrate cut to obtain an image of the section of the substrate including the plurality of thin film patterns; and measuring dimensions of a predetermined part of the thin film patterns from the image of a section of the substrate including the plurality of thin film patterns.
Preferably, in the step of measuring dimensions of a predetermined part of the thin film patterns, dimensions corresponding to a track width of the thin film magnetic head are measured, and the measurement of dimensions corresponding to the track width is sequentially carried out for all the thin film patterns on the substrate cut.
Preferably, when the measurement of dimensions corresponding to the track width is sequentially carried out for all the thin film patterns on the substrate cut, a position of a thin film pattern to be measured next is estimated from positional information of the thin film pattern measured previously.
Preferably, the result of the measurement of dimensions of a predetermined part of the thin film patterns is recorded on a schematic diagram for the thin film patterns on the substrate.
Furthermore, the present invention is characterized by an inspecting apparatus for a thin film magnetic head comprising: an illumination optical system for irradiating with illumination light a group of thin film magnetic head elements separated by cutting a substrate formed with a plurality of thin film patterns corresponding to a plurality of thin film magnetic head elements; image obtaining means for image-picking up the group of thin film magnetic head elements irradiated with illumination light by the illumination optical system to obtain an image of the group of thin film magnetic head elements; dimensions measuring means for processing the image of the group of thin film magnetic head elements obtained by the image obtaining means to sequentially measure dimensions of a predetermined part of the plurality of thin film patterns of the group of thin film magnetic head elements; and selection means for selecting a group of good thin film magnetic head elements on the basis of the dimensions of the predetermined part of the thin film patterns measured by the dimensions measuring means.
Preferably, the image obtaining means includes an objective lens for forming an image of the group of thin film magnetic head elements, and further includes a focusing optical system for focusing the objective lens into the thin film magnetic head.
Preferably, the illumination optical system irradiates the group of thin film magnetic head elements with either visible light, ultraviolet light or deep ultraviolet light, as illumination light.
Since the present invention is constituted as described above, in the production line in the GMR head forming process, high accuracy and short time measurement of a track width in the state formed to be bar-like become enabled, and it is possible to monitor the circumstances of the element forming steps in the in-process. Further, mapping in the wafer state is possible, and inconvenience of the process in the element step is found early to improve a process parameter whereby occurrence of inferior goods can be reduced, and high yield can be maintained.
These and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings.